I'm looking at google and wishing I could go check out the places that are coming up! Visiting garden centers/plant stores is one of my favorite pastimes. Too bad you're a few countries too far north from me...
I'm in the same boat about seeds, I tend to buy them when I travel but luckily we have some good local suppliers.
there's a place in Cuernavaca called Huerté organico that looks really interesting.
https://huarte-organico-1.ueniweb.com/
Hopefully someone in Mexico will chime in with some recommendations for online stores.